1. Field of the Invention
The present invention relates to an ink jet recording apparatus as well as an ink jet recording head employable for the ink jet recording apparatus. Further, the present invention relates to a method for determining the ejection state of an ink jet recording head for an ink jet recording apparatus of the foregoing type.
2. Description of the Related Art
Many proposals have been hitherto made with respect to a recording apparatus for performing a recording operation for a recording medium such as paper, a sheet of material for OHP or a similar material (hereinafter referred to as a recording paper sheet or a paper sheet) in such a manner that a recording head operable in accordance with a various kind of recording system is mounted on the recording apparatus. The recording head for the recording apparatus is typically exemplified by a wire dot type recording head, a heat susceptible type recording head, a thermal image transferring type recording head and an ink jet type recording head.
Among the aforementioned conventional recording heads, sincere attention has been paid to the ink jet type recording head adapted to eject ink directly to a recording paper sheet because it is operated at a low running cost without any generation of noisy sound.
Since the ink jet type recording head having a plurality of fine ink ejection ports arranged thereon is generally employed for an ink jet recording apparatus of the foregoing type, in the case that gas bubbles or dust particles are involved in each ink ejection port or in the case that ink fails to be ejected from each ink ejection port of the recording head due to its increased viscosity caused by evaporation of an ink solvent or the ink is transformed to assume another state unsuitable for performing a recording operation therewith, a measure is taken such that factors associated with improper ink ejection are obviated by refreshing the ink (the foregoing measure is called an ejection recovering treatment).
This ejection recovering treatment is practically executed in accordance with the following manner. Specifically, ejection recovering treatment is executed such that an element for generating energy to be utilized for ejecting ink from each ejection port of the recording head is activated while a suitable ink receiving member is disposed opposite to the ejection port forming surface of the recording head so that ink is properly ejected from each ejection port of the recording head (this type of ejection recovering treatment is called preliminary ejection treatment). Otherwise, ejection recovering treatment is executed such that while the ejection port forming surface of the recording head is covered with a cap or the like, a certain intensity of sucking force is exerted on each ejection port of the recording head so as to allow a certain quantity of ink to be forcibly discharged from each ejection port of the recording head for the purpose of eliminating factors associated with improper ink ejection (this type of ejection recovering treatment is called suction recovering treatment).
In this connection, it is preferable that improper ink ejection detecting means is disposed in association with the aforementioned ejection recovering treatment. Since a large quantity of ink is consumed for executing the suction recovering treatment compared with the preliminary ejection treatment, it is desirable to employ the suction recovering treatment only in the case that the improper ejection factor which can not be eliminated by executing the preliminary ejection treatment is employed. To this end, it is recommendable that a measure is taken in such a manner as to enable the fact that ink is not ejected from the recording head to be detected. Such a measure as mentioned above has been hitherto taken such that an optical sensor is disposed at a side of the ink flying path in order to detect whether or not ink is ejected from the recording head. With respect to a recording head of the type utilizing thermal energy used therefor as energy to be utilized for ejecting ink therefrom, since the working temperature of the recording head is undesirably elevated when a thermal energy generating element is activated while ink is not ejected from the recording head, it is acceptable to determine based on detection of the elevated temperature of the recording head in which ink is not ejected from the recording head. However, in the case that the optical sensor is disposed in that way, there arises a malfunction that the whole structure of an ink jet recording apparatus is enlarged. On the contrary, in the case that the thermal energy generating element is employed in the aforementioned manner, since detection of failure of ink ejection is indirectly executed, there is a fear that it is impossible to quickly and exactly detect that ink is not ejected from the recording head.
On the other hand, with respect to detection of a quantity of remaining ink to be supplied to an ink jet recording head, in the case that a conventional open type ink tank, mainly, an ink tank having ink impregnated in a sponge material received therein is used for the ink jet recording head, the presence or absence of ink in the ink tank is determined by penetrating an electrical conductive needle into the sponge material to check the present electrical conductive state of the needle based on the variation of a resistance value of the sponge material. Otherwise, when a closed type ink tank having an ink bag received therein is used for the ink jet recording head, a negative pressure sensor is disposed in a flow path of the ink tank to check whether a certain quantity of ink remains in the ink tank or not. However, in the case that the open type ink tank is employed for the ink jet recording head, since it is necessary to insertably dispose the electrical conductive needle in the ink tank, causing a wiring member to be additionally disposed for the ink jet recording head, there sometimes arises an occasion that not only the ink tank or the ink jet recording apparatus itself becomes expensive and complicated in structure but also the electrical conductive needle penetrated into the sponge material has a problem in respect of a detecting accuracy. On the contrary, in the case that the negative pressure sensor is disposed in the ink tank, the ink jet recording head has a problem that the negative pressure sensor itself is expensive, causing the ink jet recording apparatus to correspondingly become expensive. Another problem is that it is necessary to reserve a space required for disposing the negative pressure sensor in the ink tank, and moreover, an ink supply path in the ink tank becomes complicated.